In recent years, there has been an urgent demand for fuel-efficiency of automobile tires from the perspective of environmental concerns and resource protection. For safety reasons, there has also been a demand for excellent wet grip property, dry traction, and driveability of automobile tires.
Conventionally, a rubber composition containing carbon black as filler has been widely used for tires. However, when synthetic rubber and carbon black are mixed and kneaded, if the carbon black is not sufficiently dispersed, a tire prepared from such a mixture will not provide good performances such as a good low-heat buildup property.
In view of the circumstances, there has been considered a technique to cause, by reacting a certain modifying agent with a polymer, a rubber itself to have an affinity for carbon black. For example, Patent Literature 1 discloses a conjugated diene rubber prepared by reacting a certain tin halide compound, which has a good affinity for carbon black, with active ends of polymer chains each of which has an active end at one end and an isoprene block at the other end.